1. Field of the Invention
The present invention relates to a multi-chip device and a method for producing a multi-chip device.
2. Description of the Related Art
Memory storage capacity is usually provided by memory devices. To fulfill the market demands for higher storage density, memory devices have evolved into multi-chip devices (also referred to as multi-chip packages or MCPs) containing more than one memory chip in a single package. Because the increase of the memory density of memory chips may be limited, combining a plurality of memory chips in multi-chip memory devices may provide an efficient way to increase the density of memory devices according to the market demands. Also, for devices other than memory devices, an increased system density may be required such that a number of separately fabricated chips may be integrated into one device package.
In some cases, the integration of chips in a multi-chip device uses chip stacks. The single chips of the chip stack may be spaced apart from each other in order to provide a secure access to the contact pads of each chip by means of bonding equipment which may attach bond wire. The spacing between the chips may increase the total height of the chip stack and thereby may limit the number of stacked chips, for instance, due to size requirements of the package and bond wires or due to the stability of the multi-chip device.
In some cases, a multi-chip device may have a substrate with contact pads on a first surface on which two or more chips are stacked. Each of the stacked chips may have uncovered contact pads on a surface facing away from the first surface of the substrate. The stacked chips may be stacked in such a way that their contact pads are accessible by the bonding equipment. The bonding equipment may bond the contact pads on the first surface of the substrate to the contact pads of the respective stacked chips. The bond wire may require a spacing between the single chips of the chip stack, and the spacing for the bond wire may affect the overall height of the device. In some cases, the substrate contact pads may be placed on a portion of the first surface of the substrate which is uncovered by the chip stack. The area provided for the substrate contact pads may be limited. Thus, the overall number of contact pads on the first surface of the substrate may be limited, as well.
Accordingly, what is needed is a multi-chip package and a method for producing such a package which has a reduced height, allows for the stacking of an increased number of chips of a given total height, and/or allows for an increased number of contact pads on the substrate.